1331.ArrayRankTransform.cs

// 1331. Rank Transform of an Array
// Given an array of integers arr, replace each element with its rank.

// The rank represents how large the element is. The rank has the following rules:

// Rank is an integer starting from 1.
// The larger the element, the larger the rank. If two elements are equal, their rank must be the same.
// Rank should be as small as possible.

// Example 1:

// Input: arr = [40,10,20,30]
// Output: [4,1,2,3]
// Explanation: 40 is the largest element. 10 is the smallest. 20 is the second smallest. 30 is the third smallest.
// Example 2:

// Input: arr = [100,100,100]
// Output: [1,1,1]
// Explanation: Same elements share the same rank.
// Example 3:

// Input: arr = [37,12,28,9,100,56,80,5,12]
// Output: [5,3,4,2,8,6,7,1,3]

public class Solution {
    public int[] ArrayRankTransform(int[] arr) {
        Dictionary<int,int> rankMap = new Dictionary<int,int>();
        int[] result = new int[arr.Length];
        int[] cloneArr = (int[])arr.Clone();
        Array.Sort(cloneArr);
        int Rank = 1;
        foreach(var item in cloneArr){
            if(!rankMap.ContainsKey(item)){
                rankMap[item] = Rank++;
            }
        }
        for(int i = 0; i<arr.Length; i++){
            result[i] = rankMap[arr[i]];
        }
        return result;
    }
}